Dewaxing process with 2-stage sulfur treatment



This invention relates to improved procedure for preparing paraffin wax.

Paraflin wax is known to occur in petroleum oils in varying amounts. Itis known that this wax occurs in several forms including amicrocrystalline form which has unusual value because of its relativelyhigh tensile strength. These waxes can be separated by treating thepetroleum oil with various solvents, usually in conjunction withcooling. For instance, it is known to add methyl ethyl ketone or pentaneto the petroleum oil or heavy fraction thereof and cool to cause the waxto precipitate.

This invention has for its object to provide procedure for manufacturingparaffin wax from petroleum crudes or heavy fractions thereof. Anotherobject is to provide improved procedure whereby the yield ofmicrocrystalline wax is increased. Another object is to improve thestate of the art. Other objects will appear hereinafter.

These and other objects of our invention are accomplished by addingelemental sulfur to a petroleum crude or fraction thereof, heating themixture to a temperature above about 125 C. and thereafter separating aparaffin wax from the treated crude or heavy fraction thereof, saidparafiin wax being formed by reaction between the elemental sulfur andhydrocarbon components of the crude or heavy fraction thereof.

In the following examples and description we have set forth several ofthe preferred embodiments of our invention, but it is to be understoodthat they are given by way of illustration and not in limitationthereof.

The crude or heavy fraction thereof which may be employed in our processmay be derived from any source and may comprise any of the various typesof petroleum. Thus the crude may be a paraffin type of crude obtained inthe Pennsylvanian or other eastern areas of the United States.Alternatively, it may be a naphthenic type crude such as obtained on thewest coast of the United States or in the Mid-East. Alternatively thecrude may be one of the Mid-Continent type similar to that obtained inthe Mid-Continent portion of the United States. Such Mid- Oontinentcrudes are primarily a mixture of naphthenic and paraftlnic components.When the crude or heavy fraction thereof contains paraflin wax which isnaturally present therein, we prefer for the reasons pointed outhereinafter to first remove the parafiin wax before reaction withelemental sulfur. However, such removal is not necessary, and theparaffin wax may be left in and be present during the reaction with thesulfur. However, this mode of operation decreases the overall yield ofparaflin wax obtained from the crude. Also while the entire crude may betreated, we prefer to subject the crude to distillation to remove asdistillate components of a low boiling nature and preferably to removeall components including heavy gas oil and lighter components. The heavyresidue thus obtained is reacted with the sulfur.

The sulfur may be added in amounts between about 0.01 and 10 percent.Amounts of 0.1 to 3 percent by weight are preferred. Amounts larger thanapproximately 1 percent do not readily dissolve in the oil so that wheresuch larger amounts are employed, the mixture of sulfur and hydrocarboncharge stock should be agitated during the heat treatment in order toobtain e State Paw ICC intimate contact between all of the sulfur andthe hydrocarbon. Of course the sulfur should be in finely divided formto obtain intimate contact between the reactin components.

The mixture is heated to a temperature between about and 300 C. andpreferably a temperature between about and C. We have found that at atemperature of about 150 C. the maximum rate of reaction between thesulfur and the hydrocarbon components to form paraffin wax takes place.Also we havefound that a second maximum rate of reaction takes place ata temperature of about 225" to 250 C. This second reaction is evidentlybetween a different type of component since it results in .a largeramount of non-microcrystalline paraffin wax than the temperature in theneighborhood of 150 C. Therefore, as will be explained in more detaillater, we prefer to operate the reaction in two stages; first heating to150 C. more or less to form one type of wax which is removed, thenheating to about 225..to 250 C. to form a different type of wax which isremoved. In this mode of operation an additional amount of sulfur willbe added to the oil prior to the second stage heat treatment ifsubstantially all of the sulfur has been reacted with the oil in thefirst stage. However, if such reaction is incomplete, which will be thecase when larger amounts of sulfur are used, such second addition "ofsulfur is unnecessary. 1

The time of reaction may be between about fifteen minutes and eighthours. A heating period of between about one-half and three hours isadvantageous. '..Tlie heat treatment may be carried out in a batchmanner preferably with agitation or stirring for the reasons pointed outabove. Alternatively, the process may be carried out continuously inwhich case the mixture will be continuously passed through a heatedchamber such as a heated tubular furnace or an elongated heated reactionchamber. The products flowing from the chamber are then treated forremoval of the paraffin wax. If desired, the unreacted hydrocarbon maybe recycled for reuse in the process. Pressure does not have a materialeffect on the process. Therefore the reaction may be and is,advantageously carried out at atmosphere pres- EXAMPLE 1 One percentsulfur was added to Redwater crude oil containing 3.89 percent waxhaving the wax composition shown in Table 1, line 1. The mixture wasintroduced into a reaction bomb which was cooled to a low temperatureand subjected to vacuum for removal of air. The bomb was sealed and wasthen introduced into a furnace and heated to a temperature of 150 C. fora period of 3 hours. Thereafter the bomb was rapidly cooled tobelow 100C., the contents of the bomb were removed and analyzed for wax contentand wax composition. The total wax content was found to be 11.84percent. The wax was found to be substantially free of sulfur compounds.Its composition is given in Table I, line 2.

' l I l 3 EXAMPLEZ In another experiment, one percent sulfur was addedto the same Redwater crude described in Example 1 and the mixture wassubjected to the identical treatment except that a temperature of 238 C.was employed during the three hour heating period. The resultant wax wasseparated from the treated crude in an amount of 8.33 percent. The waxwas analyzed and the composition of this wax is shown in Table II.

Table II WAX COMPOSITION Non-Con- Con- Alkanes densed densed Alkyl Naph-Gyclo- Oyclo Benzenes thalencs alkanes alkanes 'microcrystalline wax,while the higher temperature product has a higher content of thematerial ordinarily called For these reasons we have found it to beadvantageous to react the crude with the sulfur at a temperature in theneighborhood of 150 C. such as 150 to 170 C. to obtain a higher contentof microcrystalline wax, to separate the wax thus produced, and to thenrepeat the same operation at a temperature of about 225 C. to 250 C. andthereafter separate a wax containing a higher content of ordinary waxcomponents. Since the wax naturally present in the crude reacts withsulfur to a certain extent, we also prefer to treat the crude forremoval of the naturally contained wax prior to reacting with sulfur. Inall of these wax removal procedures, any known or conventionally usedwax removal procedure such as chilling in the presence of methyl ethylketone, pentane, etc. may be employed.

We claim:

1. The process for preparing paraffin wax in high yield which comprisesin combination adding between about 0.01 and 10 percent sulfur to amember of the group consisting of crude petroleum and high boilingfractions of crude petroleum, heating the mixture to a temperaturebetween about and C., subjecting the reaction product to treatment forremoval of a first portion of paraflin wax high in microcrystallinecomponents, adding between about 0.01 and 10 percent elemental sulfur tothe crude from which the parafiin wax formed during the precedingtreatment has been removed, heating the mixture to a temperature ofbetween about 225 and 250 C. and removing a second portion of parafiinwax, said second portion containing a lower percentage ofmicrocrystalline components than the first portion of paraflin wax.

2. The process for preparing paraffin wax in high yield which comprisesin combination subjecting a member of the group consisting of crudepetroleum which contains paraflin wax and high boiling fractions ofcrude petroleum which contain parafiin wax to a treatment for removal ofa first portion of parafiin wax naturally contained therein, addingbetween about 0.1 and 3 percent elemental sulfur to the portion freed ofparafiin wax, heating the mixture to a temperature of between about 150and 170 C., subjecting the reaction product to treatment for removal ofa second portion of parafiin wax which contains a relatively largeamount of microcrystalline components, adding between about 0.1 and 3percent elemental sulfur to the crude from which the paraflin wax formedduring the preceding treatment has been removed,

.heating the mixture to a temperature of between about 225 and 250 C.and removing a third portion of paraflin wax, said third portioncontaining a lower percentage of microcrystalline components than thesecond portion of paraflin wax.

References Cited in the file of this patent UNITED STATES PATENTS1,809,777 Edeleanu June 9, 1931 2,026,336 Wilson Dec. 31, 1935 2,142,916Parkhurst Jan. 3, 1939 2,432,440 Patterson Dec. 9, 1947

1. THE PROCESS FOR PREPARING PARAFFIN WAX IN HIGH YIELD WHICH COMPRISESIN COMBINATION ADDING BETWEEN ABOUT 0.01 AND 10 PERCENT SULFUR TO AMEMBER OF THE GROUP CONSISTING OF CRUDE PETROLEUM AND HIGH BOILINGFRACTIONS OF CRUDE PETROLEUM, HEATING THE MIXTURE TO A TEMPERATUREBETWEEN ABOUT 150* AND 170*C., SUBJECTING THE REACTION PRODUCT TOTREATMENT FOR REMOVAL OF A FIRST PORTION OF PARAFFIN WAX HIGH INMICROCRYSTALLINE COMPONENTS, ADDING BETWEEN ABOUT 0.01 AND 10 PERCENTELEMENTAL SULFUR TO THE CRUDE FROM WHICH THE PARAFFIN WAX FORMED DURINGTHE PRECEDING TREATMENT HAS BEEN REMOVED, HEATING THE MIXTURE TO ATEMPERATURE OF BETWEEN ABOUT 225* AND 250*C. AND REMOVING A SECONDPORTION OF PARAFFIN WAX, SAID SECOND PORTION CONTAINING A LOWERPERCENTAGE OF MICROCRYSTALLINE COMPONENTS THAN THE FIRST PORTION OFPARAFFIN WAX.